1. Field of the Invention
This invention involves an arrangement for smooth and continuous feeding of pressurized blasting material, in particular, for feeding blasting powder in abrasive dental devices.
2. Description of the Related Art
The whine of the dentist's drill is one of the most unwelcome sounds in the modern world. A standing goal in dentistry is therefore to find a way to efficiently and precisely reduce a tooth, for example, in preparation for a filling, or to remove plaque, with as little discomfort to the patient as possible.
One promising alternative to the conventional rotating or vibrating mechanical drill bit is a tool that directs a fine stream of a pressurized abrasive powder against the surface of the tooth. Experience has indicated that these devices cause much less trauma to the tooth yet are at least as effective at removing tooth enamel as a conventional drill head. Moreover, since there is no hard physical contact between the surface of the tooth and a fast-vibrating or rotating drill bit or head, blasting systems also reduce the risk of chipping the tooth surface.
The general technique of treating teeth using an abrasive jet is described in the following publications:
"Technic for Nonmechanical Preparation of Cavities and Prophylaxis," Robert Black, Journal of the American Dental Association, Vol. 32, pp. 955-965, 1945;;
"Airbrasive: some fundamentals," Robert Black, Journal of the American Dental Association, Vol. 41, pp. 701-710, 1950;
"Airbrasive Technic Discussed," Harold Roach, Journal of the American Dental Association, Vol. 43, p. 108, 1951; and
"Analysis of airbrasive procedures in dental practice," Sidney Epstein, Journal of the American Dental Association, Vol. 43, p. 578, 1951.
Known devices for treating teeth with an abrasive jet include those described in:
U.S. Pat. No. 2,696,049 (Black, Dec. 7, 1954);
U.S. Pat. No. 3,852,918 (Black, Dec. 10, 1974);
U.S. Pat. No. 4,412,402 (Gallant, Nov. 1, 1983);
U.S. Pat. No. 4,522,597 (Gallant, Jun. 11, 1985);
U.S. Pat. No. 4,635,897 (Gallant, Jan. 13, 1987);
U.S. Pat. No. 4,708,534 (Gallant, Nov. 24, 1987);
U.S. Pat. No. 4,733,503 (Gallant, Mar. 29, 1988);
U.S. Pat. No. 4,893,440 (Gallant et al., Jan. 16, 1990);
U.S. Pat. No. 5,275,561 (Goldsmith, Jan. 4, 1994);
U.S. Pat. No. 5,330,354 (Gallant, Jul. 19, 1994);
U.S. Pat. No. 5,334,016 (Goldsmith, Aug. 2, 1994);
U.S. Pat. No. 5,350,299 (Gallant, Sep. 27, 1994); and
International (PCT) Patent Application, Publication No. WO 93/10718 (Goldsmith, published Jun. 10, 1993).
Known devices such as these suffer from one or all of the following disadvantages:
1) their delivery rates vary greatly depending on how full their reservoirs are, which in turn means they are harder to control accurately;
2) they don't keep the blasting material, such as abrasive powder, properly stirred and fluidized (in the device described in auger-fed U.S. Pat. No. 4,708,534 device, for example, big particles may tend to remain in the vessel);
3) they have many parts, which makes them hard to manufacture and expensive; and
4) they are not self-cleaning, so that feeding nozzles often become clogged.
What is needed is a feeding device that overcomes these disadvantages.